[Bug 1982583] Re: Fix for zlib CRC32 optimization for s390x

[Simon Chopin]

Folded into the LP #1990379 uploads to Jammy, Kinetic and Lunar.

** Also affects: zlib (Ubuntu Jammy)
   Importance: Undecided
       Status: New

** Also affects: zlib (Ubuntu Kinetic)
   Importance: Undecided
       Status: New

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Title:
  Fix for zlib CRC32 optimization for s390x

Status in Ubuntu on IBM z Systems:
  In Progress
Status in zlib package in Ubuntu:
  In Progress
Status in zlib source package in Jammy:
  New
Status in zlib source package in Kinetic:
  New

Bug description:
  SRU Justification:
  ------------------

  [ Impact ]

   * There were two issues identified in the current
     zlib CRC32 optimization for s390x implementation:

   * 1) s390_crc32_vx() signature mismatch
        which causes a warning

   * 2) '-DS390_CRC32_VX' was not added to SFLAGS
        which results in vectorization being enabled only in the static library.

   * The fixes are quite small and affect each only one line:

   * 1) by using unsigned longs instead of uint32_t in s390_crc32_vx
  declaration

   * 2) by add line 'SFLAGS="$SFLAGS -DS390_CRC32_VX"'

  [ Test Plan ]

   * An affected Ubuntu release ([20.04], 22.04 and 22.10) installed
     on a z15/LinuxONE III or newer system is needed.

   * Then it's possible to test the updated package with the help
     of a small test program (in C) that checks for
     s390_crc32_vx() signature mismatches.

   * The bug reporter has a set of s390x-specific tests that will be
  executed.

   * Test will be done by IBM.

  [ Where problems could occur ]

   * The fixes are each limited to one line, hence there are
     not many issues to expect, other than:

   * Typos (e.g. in the flags), mixing of CFLAGS and SFLAGS,

   * in case the changed data type in s390_crc32_vx is causing issues
     inside of s390_crc32_vx or in other parts of the code.

   * Structural and syntactical issues can be identified with a test build
     that was done for all affected Ubuntu releases and for all major archs:
     https://launchpad.net/~fheimes/+archive/ubuntu/lp1990379+lp1982583

  [ Other Info ]

   * This bug (LP#1982583) is solved in combination with LP#1990379,
     so that only one package update is needed.
     However, LP#1990379 also affects Focal, but this bug only Jammy and Kinetic.

   * To fix LP#1990379 also for focal the debdiff mentioned there is needed, too.
  __________

  'zlib CRC32 optimization for s390x works only in a static library'

  I've discovered two issues in lp1932010-ibm-z-add-vectorized-
  crc32-implementation.patch:

  1) s390_crc32_vx() signature mismatch, resulting in a warning.
  2) -DS390_CRC32_VX is not added to SFLAGS, resulting in vectorization being enabled only in the static library.

  I've attached the updated patch.

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